Preheat oven & prepare dish: Preheat the oven to 180°C / 350°F. Lightly grease a baking dish with a bit of sausage grease or butter.
Sauté bell pepper: Heat the remaining sausage grease in a skillet over medium-high heat. Add diced bell pepper and sauté 2–3 minutes until softened and fragrant. Season lightly.
Prepare hash browns: Peel and grate the potatoes. Squeeze out excess moisture by gathering a handful at a time and pressing firmly over the sink.
Cook potatoes with peppers: Add the drained potatoes to the skillet with bell pepper. Sauté 2–3 minutes until slightly softened. Season generously with salt and pepper.
Layer base: Spread the potato and bell pepper mixture evenly in the prepared baking dish. Top with sliced cooked sausage (any type you like).
Mix eggs & cheese: In a bowl, whisk together eggs, milk, onion powder, salt, and pepper until smooth. Stir in 1 cup shredded Cheddar.
Assemble casserole: Pour the egg and cheese mixture evenly over the potato, pepper, and sausage layer. Sprinkle the remaining Cheddar on top.
Bake & rest: Bake for 30–40 minutes, until the center is set and the top is golden and slightly crispy. Let rest 10 minutes before slicing and serving.